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NAVIGATION
By Capt. Dan Berg
 Most wreck dives are done from a boat, anchored above the site.
Depending on visibility and currents, it can be at times difficult
to find the anchor line once the dive is over. The end result of not
returning to the anchor line could be a long surface swim back to
the boat or if the diver has exceeded the no decompression limits, a
free floating hang. Here are a few helpful hints for navigation
around a wreck. First, as with any boat dive, divers should try to
start their dive into the current; this will make for an easier swim
when returning. If the wreck is intact and the visibility is good,
it is often no problem to simply note where you are and return
later, but if visibility is limited or if the wreck is scattered
over a large area with no distinct reference points, divers can use
a tether line reel, clipping one end on or near the anchor while
letting line out as they swim to explore the wreckage. This is
almost foolproof because as long as the line is not severed, you can
easily return to your starting point. Although this is very safe and
dependable, this method does have its disadvantages, one of which is
the way it limits a diver's investigation to the length of the line,
and the same territory must be covered during the second half of the
dive. When using this navigational tool, be careful not to let too
much line out as you swim. During a visit to the wreck of a German
submarine,
U-853, last year, I watched in amazement as two
self acclaimed good wreck divers let yards and yards of extra nylon
line escape from their reel. This line drifted into other divers and
tangled up an entire area of the wreck. In fact, it was so bad that
the divers could not even use the line to find their way back. Aside
from not getting any navigational benefit from their tool, these
divers ended up cutting the line and leaving it behind on the site.
The line would have stayed their for years causing a nuisance to all
if it hadn't been cut and removed by two other divers.
 The misuse of the tether line is compounded when you realize that
this wreck is intact and upright. Submarines are long and skinny. As
long as you take note of where the anchor is set, it's almost
impossible not to be able to find it, without a line. Each wreck is
different, and each diver's capabilities are different. Use these
navigational aides when they are needed, and it will enhance your
enjoyment of the sport.
Another commonly used method is the perimeter search in which a
diver descends on the anchor line and then swims directly to either
side of the wreck. The next step is to take note of a unique feature
or characteristic and the relative position, then swim up current
while exploring, spear fishing, taking photos or whatever is
desired. When you want to return, simply swim down current along the
wreck's side until you see the same object or road sign. Lastly,
swim towards the center of the wreckage where you should be able to
find the anchor.
Other methods include attaching a small strobe light to the anchor
line about 20 or 30 feet of the bottom. Divers can then freely
explore the wreck as long as they remain in site of the strobe
light.
After a while navigation becomes second nature; the more dives you
do, the better you become. Also, the more dives you do on each
wreck, the better the picture in your head becomes as to the wreck's
layout. Pretty soon you will recognize parts of the ship and their
location in relationship to other areas of the wreck. After many
excursions to the same wreck, you will be able to navigate simply
from your own knowledge of the area.
If the anchor happens to come loose or you can't find it, you can
use your tether line reel, or Jersey reel as an up line. One way to
use the reel is to attach a lift bag to the end and send it to the
surface. Be sure that your reel is free spinning, or it may pull out
of your hands. The line is then tied to the wreck and cut. This
method also provides a surface marker and acts as your own personal
anchor line. The second method is to just attach the loose end of
the reel to the wreck and un-reel the line as you ascend.
Some shipwrecks are located, in shallow water close to shore.
Navigation on these wrecks involves how to find them and how to get
back to shore when the dive is over. First of all, whether someone
has told you of a wreck or you just stumble in to one, it is a good
idea to take note of its location so you can return. You have to
pick at least two objects on the shore at approximately 90 degrees
and note how they line up with objects behind them. For example, a
telephone pole lines up with the right side of a house, and a water
tower's right side just touches a building's left corner. You will
note how accurate these ranges are by swimming a few feet in each
direction and noting how each range changes. From now on, all you
have to do is to navigate to those ranges, descend, and the wreck
should be found again. The next step is to take a compass course to
your shore entry point and after your dive, navigate to it. Be sure
to count each fin kick and make a mental note of the total. I have
always found it easier to navigate to a wreck underwater. With the
reciprocal of the compass course and the number of kick cycles, you
may navigate easily out to the site. Depending on any current and
your ability to use a compass accurately, you should swim directly
to the wreck. If this fails, you can always surface and use the land
ranges before descending again.
Many shipwrecks located close enough to shore for beach dives are
popular for night dives and
lobstering. When you surface above the
wreck at night, many times the shoreline with all the street and
city lights looks remarkably consistent. The use of a flashing light
similar to a road hazard light can vividly mark your exact entry
point. This little trick may save a long walk to return to your car.
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The Shipwreck Diving E-Book
Instant Downloadable E-Book
Shipwreck Diving,
by Capt. Dan Berg is a complete how to book about the sport of
wreck diving. This book is packed with information and heavily
illustrated with over 80 sensational color photographs. |
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